Security of the packages is important, since product counterfeiting is a multi billion business and the brand owners lose annually large sums of money with counterfeit products. For example in the US alone more than 1.2 billion DVDs are sold every year. In packages, the most common security solution is the hologram, which is however relatively easy to counterfeit. Typical application areas for holograms are e.g. tamper evidence, brand protection and authentication.
Monitoring of products own security is also important for perishable articles. This is especially important for safety of pharmaceutical products, food, food additives, cosmetics, chemicals or other such products, where the European Union directive requires manufacturers to notify the expiration date of the product usage, i.e. when the useful life of the perishable product lapses, in product packaging. If the perishable product is actually exposed to harmful stimulus being higher/lower than a certain threshold, where the stimulus is caused by physical or chemical phenomenon including mechanical, radiative or other environmental phenomena, the product may degrade or spoil before the calculated expiration date. For example, product's cold chain management needs actual real-time detection of exposure to harmful stimulus through the supply chain to indicate that the product is usable or not.
Surface sensor indicators for food and medical package applications have been on market since 1970-80's. Time and time-temperature indicators are known which operate by chemical reaction mechanism, diffusion mechanism, and capillary driven fluid wicking mechanism, e.g. migration of fluids or gels through wicks to indicate the passage of time or thermal exposure. There are known time and time-temperature indicators that function by flow of a material through channels of the microstructured substrate.
Liquid based time indicators are used for monitoring product safety and quality. Labels to be sticked on products contain a liquid dye which, when activated, migrates across the label at a consistate rate. They are activated by squeezing a start button which moves the liquid into direct contact with a porous membrane through which the liquid diffuses. Labels can be tailored to different time periods. However, liquid based time indicators monitor only time but not product adelturation directly. Time-temperature indicators may operate by chemical reaction, diffusion or capillary driven fluid-wicking mechanism. The label comprising time-temperature indicators reacts to temperature changes and time of exposure of the product to temperatures exceeding a critical temperature. In time-temperature indicators two reagents are diluted and placed in two neighbouring beds where the two solutions are immobilised. Above the critical temperature (freezing the solutions) the structure that immobilises the solutions is damaged and exposure to a given temperature during suitable time (melting the solutions), the solutions are no longer immobilised and they can intermingle causing a reaction which is visible. However, time-temperature indicators react to changes in temperature and time in storage conditions only.
Attempts have also been made to use electronic devices employing a temperature measuring probe and a microcontroller to make it possible both to detect when the temperature is exceeded and for how long. For indicating the result there is also needed a radio frequency transmitter or optical transmitter, e.g RFID or LED device. However, such electronic devices prove to be expensive to be used systematically on all the product items for which it is wished to monitor the temperature. There is also a disadvantage that the electronic circuits such as the sensor probe, microcontroller and transmitter have to be powered by a battery which is expensive and difficult to implement on a disposable product label.
Referring to FIG. 1 there is depicted an electronic time indicator according to the prior art as disclosed in WO 2008/107871 A1. This electronic indicator can be used as a promotional device providing the user with predetermined information as well as a time dependent product monitoring device. On a substrate layer 12 with displays 18 is a battery 14, a controlling chip 17 and electrical conducting connectors 19. The displays 18 can be e.g. organic light emitting diodes (OLED) that is manufactured e.g. by ink jet printing. The battery 14 can be e.g. a printed paper battery or thin button cell battery. The printed paper battery can be construed using a cathode that is deposited by printing, stamping and sputtering, and an anode that is deposited by printing and stamping, and an electrolyte in a form of a gel and polymer being enclosed in a plastic barrier material to prevent loss of moisture. Electrical conducting connectors 19 pass electrical signals and electrical power from the battery 14 and the controlling chip 17 to the displays 18. Such electrical conducting connectors 19 can be formed onto the substrate layer 12 by ink jet printing, rotary screen printing, etching and other methods known in the art. The controlling chip 17 is positioned directly on to the electrical connectors 19 by dye bonding and flip chip method and it selectively switches power from the battery 14 to the displays 18. A switch 15 is located on a top layer 11 as well as transparent windows 16 for viewing the displays 18. The switch 15 can be a membrane switch, sticky switch, collapsible switch and a removable insulator known in the art. The substrate layer 12 is made of laminatable material such as paper, PVC and PET and the top layer 11 is made of laminatable material such as PP, PVC and PET. The electronic time indicator device is activated by suppressing the switch 15 which closes contacts 13 between the battery 14 and the chip 17 allowing electricity to flow between the battery 14 and the chip 17. Upon activation the counter within the chip 17 begins to count. When the count equals to the pre-registered count constant, then the chip 17 opens an internal electrical gateway allowing electricity to pass from the battery 14 to one of the displays 18 thus causing a visible change in the optical properties of said display 18. Different counts can be pre-registered for each one of the displays 18. However, this kind of electronic indicator has to be manually activated and it only relies on counted time and therefore it does respond to actual exposure to harmful stimulus of physical, chemical or other environmental phenomena. Further, it requires the battery which is expensive and difficult to implement on a disposable product label.
Therefore, there is a need for an indicator structure that is easily and reliably attachable to monitored products and/or packages. There is also a need for an indicator structure that offers easy and reliable security solution to prevent product counterfeit. Furthermore, there is a need for an indicator structure comprising electronic and/or other circuits that does not require complicated and expensive arrangements to supply power to electronic and/or other circuits requiring energy supply. Furthermore, there is a need for an indicator structure that is easy and cost-effective to manufacture. Furthermore, there is a need for an indicator structure for multifunctional use in tamper evidence, authentication, safety monitoring, promotional, etc. purposes.